KR100594660B1 - Reflection type liquid crystal display device - Google Patents

Abstract

In a reflective liquid crystal display device having a front light and a reflective liquid crystal panel including a reflective electrode having a concave-convex structure, the incident light from the front light is directed in a vertical direction by varying an average inclination angle of the concave-convex structure of the reflective electrode. And a high viewing angle reflecting region having a characteristic of reflecting light in a vertical direction, and a wide viewing angle reflecting region having a characteristic of reflecting external light incident at an oblique angle in a vertical direction, wherein the high directivity reflecting region and the wide viewing angle reflecting region are the same display device. It is formed by mixing in the reflection electrode inside.

Reflective liquid crystal display, front light

Description

Reflective liquid crystal display device {REFLECTION TYPE LIQUID CRYSTAL DISPLAY DEVICE}

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view showing the configuration of one display device of a reflecting plate used in a reflective liquid crystal display device according to an embodiment of the present invention.

2 is a diagram showing reflection characteristics of a reflecting plate used in a reflective liquid crystal display device according to an embodiment of the present invention;

Fig. 3 is a diagram showing the luminance when the front light of the reflector is used for the reflective liquid crystal display device according to the embodiment of the present invention.

4A to 4D are cross-sectional views of a reflecting plate for explaining a method for manufacturing a reflecting area according to an embodiment of the present invention.

5A and 5B are views for explaining the operation mechanism of the reflector used in the reflective liquid crystal display device according to the embodiment of the present invention.

Fig. 6 is a plan view showing the configuration of a reflecting plate used in a reflective liquid crystal display device according to an embodiment of the present invention.

7 (a) and 7 (b) are diagrams for explaining the second operation mechanism of the reflector used in the reflective liquid crystal display device according to the embodiment of the present invention.

Fig. 8 is a plan view showing a second configuration of one display device of the reflecting plate used in the reflective liquid crystal display device according to the embodiment of the present invention.

9 (a) and 9 (b) are diagrams for explaining the operation mechanism of the reflector according to the second embodiment of the present invention.

10 is a cross-sectional view showing the configuration of a reflective liquid crystal panel, a reflector and a front light according to the prior art;

Fig. 11 is a plan view showing the configuration of a reflective liquid crystal panel, a reflector and a front light according to the prior art;

12 is a view showing the outgoing light characteristics of the front light according to the prior art.

13A and 13B show reflection characteristics of a reflecting plate used in a reflection type liquid crystal display device according to the prior art.

♠ Explanation of the symbols for the main parts of the drawings.

1 reflective electrode 2 display device

3: high directional reflection area 4: wide viewing angle reflection area

5: TFT area 6: TFT substrate

7: organic insulating film 8: mask

9: uneven structure 10: outside light

11: light from the front light 12: prism groove

13: color filter 14: high transmittance color filter

15: high color gamut color filter 16: front light

17 reflection type liquid crystal panel 18 light source unit

19 pixels

The present invention relates to a reflective liquid crystal display device, and more particularly to a reflective liquid crystal display device having a front light.

Conventional technology

Background Art [0002] Reflective liquid crystal display devices are employed in mobile phones, personal digital assistants (PDAs), and the like, because of the advantage that the backlight does not always need to be turned on and is suitable for low power consumption.

In the case of a reflective liquid crystal display device, the display is mainly performed by using light from external light, but it is often provided with an auxiliary light source called a front light assuming use in an environment where external light cannot be expected. Hereinafter, the basic configuration of the reflective liquid crystal display device having the front light will be described.

10 and 11 show the configuration of a reflective liquid crystal panel and a front light according to the related art. The reflective liquid crystal panel 17 includes a liquid crystal layer 173 inserted between the pixel substrate 171 including the reflective pixel electrode and the color filter substrate 172.

As shown in FIG. 10, the front light 16 is disposed on the front side (observer side) of the reflective liquid crystal panel 17, and the light from the light source unit 18 is incident on the reflective liquid crystal panel 17. And a function of transmitting the light reflected from inside the reflective liquid crystal panel 17 to the observer side.

As shown in Fig. 11, the reflective liquid crystal panel 17 has a reflective electrode 1 having a concave-convex structure for reflecting light on the TFT substrate, and red, green, blue (R) for color display. One pixel 19 is formed of three display devices 2 corresponding to, G, and B. In this case, a method of forming a random uneven pattern in one display device 2 or one pixel 19 serving as a basic unit is common.

FIG. 12 is a diagram showing a change in luminance with respect to an observation angle of the outgoing light from the front light 16. As can be seen from the figure, in order to obtain a bright display when the front light is turned on, light is emitted in a direction substantially perpendicular to the reflective liquid crystal panel 17.

13 (a) and 13 (b) show the characteristics of the reflector according to the prior art. That is, the light reception angle dependence of the reflectance with respect to parallel incident light whose incidence angle is 30 degrees is shown.

As shown in Fig. 13A, the reflective liquid crystal display device is often used outdoors, in which case the display of the liquid crystal panel is viewed using external light such as sunlight or fluorescent lamps.

However, although the brightness is the strongest at the specular reflection position of the external light, the image of the liquid crystal panel is hardly seen because the image of the external light is seen. Therefore, in the reflector according to the prior art, as shown by the arrow in Fig. 13A, the reflector is designed so that a bright display can be obtained at an angle of several tens of degrees away from the normal reflection position (30 °) of external light. Was done.

On the other hand, in the case of the reflective liquid crystal panel provided with the front light, as shown in Fig. 13B, a reflection plate focused on effectively using the light from the front light has been proposed.

In many cases, a white light emitting diode is adopted as a cold-cathode replacement from the viewpoint of low power consumption and low noise. However, since the light emitting diode has a smaller power input than the cold cathode tube, it is cold. It is difficult to obtain high brightness as compared to the cathode tube.

Specifically, the planar portion of the reflecting plate is enlarged to increase the specular reflection component so that high luminance is obtained when the front light is turned on.

As a result, as shown in Fig. 13B, a bright display is obtained at an angle close to regular reflection.

However, in the conventional reflective type liquid crystal device with a front light, high luminance is obtained when the front light is turned on, but the viewing angle is narrow, and a bright display is not obtained under external light when the front light is not lit. there is a problem.

That is, since external light and a front light have different methods of using light, that is, an optical system, there is a problem that it is difficult to obtain a bright display together in both environments in a conventional reflective liquid crystal device having a front light.

The present invention has been made under such a technical background. Accordingly, an object of the present invention is to provide a reflective liquid crystal display device capable of obtaining a bright display in any environment, such as outdoors or in a dark place where external light is dominant and lighting of a front light is required.

In order to achieve the above object, the present invention provides a reflective liquid crystal display device having a front light and a reflective liquid crystal panel including a reflective electrode having an uneven structure, wherein the same display device has an average inclination angle of the uneven structure of the reflective electrode. Has two or more reflection areas different from each other, and the at least one reflection area has a reflection characteristic of reflecting the incident light from the front light in the vertical direction.

In addition, the present invention provides a reflective liquid crystal display device having a front light and a reflective liquid crystal panel including a reflective electrode having a concave-convex structure, wherein the reflective electrode in the same display device has a reflective region and a high viewing angle reflective characteristic. It is characterized in that it is made of a reflection area having directional reflection characteristics, and the reflection area having high directional reflection characteristics has reflection characteristics for reflecting incident light from the front light in the vertical direction.

In addition, the present invention provides a reflective liquid crystal display device having a front light and a reflective liquid crystal panel including a reflective electrode having a concave-convex structure, wherein the reflective electrode in the same display device has a reflective region and a high viewing angle reflective characteristic. The average inclination angle of the concave-convex structure of the reflecting electrode of the reflecting region of the reflecting region, which is composed of the reflecting region having the directional reflecting characteristic, and the wide viewing angle reflecting characteristic, It is characterized in that it is in the range of 1.3 to 3 times.

In addition, the present invention is characterized in that the area of the reflective region having the high-direction reflective characteristic of the reflective electrode is in the range of 1 to 4 times the area of the reflective region having the wide viewing angle reflective characteristic.

Moreover, this invention is characterized by the boundary of the other reflective area | region in the reflective electrode being formed in staircase shape.

In addition, the present invention is characterized in that, in the reflective electrode in the same display device, a reflective region having high-directional reflectivity is disposed above the reflective liquid crystal panel rather than a reflective region having wide viewing angle reflection characteristics.

In the present invention, a color filter having a high transmittance is divided into a region corresponding to the wide viewing angle reflection region of the reflective electrode, and a color filter having a high chromaticity range is divided into a region corresponding to the high directional reflection region. It is characterized by being arranged.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

1 is a plan view showing the configuration of one display device 2 of the reflective electrode 1 used in the reflective liquid crystal display device according to the embodiment of the present invention. In the same figure, the black line part represents the convex part of the reflective electrode 1, The wider the black line part, the wider the flat part of the convex part top part, and the average inclination angle of the unevenness becomes smaller.

After forming the uneven shape of the reflecting plate, the average inclination angle is measured on the surface of the uneven shape by using an atomic force microscope (AFM) or the like, and the differential inclination angle is calculated from the result. It is obtained by averaging.

As shown in FIG. 1, in the design of the reflective electrode 1 used in the reflective liquid crystal display device according to the embodiment of the present invention, one display device or one display unit serving as a basic unit of a random pattern of the reflective electrode is provided. The pixel is divided into two or more regions, and the highly directional reflecting region 3 and the wide viewing angle reflecting region 4 are arranged at a predetermined area ratio.

Here, the highly directional reflective region 3 refers to a region in which the regular inclination of the concave-convex structure of the reflective electrode 1 is small, and since the flat portion is wide, the regular reflection of light is dominant.

On the other hand, the wide viewing angle reflective region 4 refers to a region where the average inclination angle of the uneven structure of the reflective electrode 1 is large and the scattering of light is strong.

Here, with respect to the angle of incidence of incident light on the liquid crystal display panel, the average inclination angle of the uneven structure of the reflective electrode 1 required to reflect the reflected light in front of the liquid crystal panel, that is, in the vertical direction, is incident from the air into the liquid crystal display panel. This can be derived from Snell's law, taking into account the change in refractive index.

First, when the front light member is used, the emitted light distribution from the front light is narrow light of ± 20 ° or less, as shown in FIG. 12, and is in a range of ± 10 ° or more and ± 20 ° or less. The average inclination angle of the concave-convex structure of the reflective electrode of the high-direction reflective region 3 necessary for reflecting the incident light having this inclination to the front of the liquid crystal display panel is derived from about 3.3 degrees to about 5 degrees.

On the other hand, in the case of using external light, it is preferable to the user to see the display from a substantially vertical direction with respect to the liquid crystal display panel. However, the user may attach the liquid crystal display panel to incident light from the light source so that light sources such as sunlight and fluorescent light do not enter the eyes. It turned out that it uses inclined by about 30 degrees from about 20 degrees.

From this, the average inclination angle of the concave-convex structure of the reflective electrode of the wide viewing angle reflective region 4 required for reflecting the incident light to the front of the liquid crystal display panel at the time of using external light is derived from about 6.5 degrees or more and about 9.5 degrees or less.

As described above, when the average inclination angle of the wide viewing angle reflection region is about 1.3 times (6.5 degrees: 5.0 degrees) to about 3 times (9.5 degrees: 3.3 degrees) of the average inclination angle of the high-directional reflection region, Bright and good display characteristics can be obtained in both environments when using external light.

In addition, in the Example of this invention, the average inclination angle of the wide viewing angle reflection area was about 7.5 degrees, and the average inclination angle of the high directional reflection area was about 4 degrees.

In addition, adjustment of an average inclination angle is based on the design of a mask pattern, the exposure energy (exposure amount 80mJ: in fact, it adjusts by exposure time) in the photoresist process, and the baking time (140 degreeC) of the uneven shape photoresist pattern. It was done by.

2 shows reflection characteristics of the reflective electrode of the reflective liquid crystal display device according to the embodiment of the present invention. The figure shows the change of reflectance by the area ratio of the wide viewing angle reflection area | region 4 with respect to the highly directional reflection area | region 3 in one display apparatus.

From the figure, it can be seen that the brightness observed at the position of 0 degrees to 20 degrees for the angle of incidence at an upper 30 degrees depends on the area of the wide viewing angle reflective region 4.

On the other hand, from FIG. 3, it turns out that the brightness | luminance at the time of turning on the front light FL depends on the area of the highly directional reflection area | region 3. In FIG. Therefore, by adjusting the area ratio, it becomes possible to adjust whether the importance of brightness to external light or the brightness at the time of front light lighting is important.

From Fig. 3, even when the area ratio of the wide viewing angle reflective region 4 to the highly directional reflective region 3 is 5: 5, the entire surface is about 95% compared with the case of the highly directional reflective region 3. It can be seen that the luminance is obtained.

On the other hand, when the area ratio of the wide viewing angle reflective region 4 to the high directivity reflective region 3 becomes 2: 8 or more, and the area of the wide viewing angle reflective region 4 becomes small, formation of the reflective electrode having a good uneven shape This becomes difficult and sufficient reflection characteristics cannot be obtained.

In view of the above, when the front light is used and the outside light is in the range of about 1 times (area ratio 5: 5) to about 4 times (area ratio 2: 8) of the area of the high-direction reflective region 3 from about the wide viewing angle reflective region 4. Bright and good display characteristics are obtained in both environments at the time of use.

In the embodiment of the present invention, the area ratio of the wide viewing angle reflective region 4 and the highly directional reflective region 3 is set to about 3: 7. By setting in this way, the brightness | luminance equivalent to the case where the whole surface of the reflecting plate 1 was made into the highly directional reflection area | region 3 at the time of front light lighting was obtained (FIG. 3). At the same time, as can be seen from FIG. 2, even when the light receiving angle is 0 degrees, when the entire surface of the reflecting plate is the highly directional reflecting region 3, the reflectance is almost zero, but the reflectance is about 10 in the embodiment of the present invention. Good reflection characteristics of more than% can be obtained.

As described above, in the embodiment of the present invention, the area ratio between the wide viewing angle reflective region 4 and the highly directional reflective region 3 is about 3 to 7, so that both the external light and the front light are turned on. Good brightness can be obtained.

Next, the manufacturing method of a reflection area is demonstrated.

An example of the manufacturing method of the reflection area | region with which the reflective characteristic which has uneven | corrugated shape differs is described in Unexamined-Japanese-Patent No. 2001-337323. According to this manufacturing method, the average inclination angle of the concave-convex shape is adjusted by changing the depth of the concave-convex shape, thereby forming a reflection area having different reflection characteristics.

However, in this manufacturing method, two different masks are required, and since it is necessary to go through two exposure steps, the manufacturing method becomes complicated, resulting in an increase in manufacturing cost.

However, the reflection type liquid crystal display device described in the above publication is based on the premise of use under external light, and there is no description regarding the case where the front light is used, and the reflection type liquid crystal display device according to the present embodiment provided with the front light. Is a different configuration.

4 is a cross-sectional view for explaining a method for manufacturing a reflective region according to the embodiment of the present invention.

First, as shown in Fig. 4A, the organic insulating film 7 is formed on the entire surface on the TFT substrate 6 having the TFT region 5. As the organic insulating film 7, for example, acrylic photosensitive resin can be used.

Next, as shown in Fig. 4B, a mask having a pattern corresponding to the wide viewing angle reflective region 4 and the highly directional reflective region 3 having a predetermined area ratio in the same display apparatus or the same pixel ( Using 8), exposure and development by ordinary photolithography are performed to form the uneven structure 9 shown in Fig. 4C.

Thereafter, the convex portion of the uneven structure 9 is melted by heat treatment to be converted into a smooth convex shape, as shown in FIG. The wide viewing angle reflection region 4 can be formed simultaneously in one process.

Finally, by forming a metal such as aluminum on the entire surface on the uneven structure 9, the reflective electrode 1 having the uneven shape is completed.

Next, with reference to FIG. 5, the operation mechanism of the reflecting plate used for the reflective liquid crystal display device which concerns on the Example of this invention is demonstrated.

As shown in FIG. 5A, a bright display can be obtained for the external light 10 at an angle deviating from the normal reflection angle due to the characteristics of the wide viewing angle reflective region 4. This is because in the case of relatively spotted point light sources such as sunlight or fluorescent lamps, a bright display can be obtained at a position deviating a few degrees from the specular reflection by the effect of the wide viewing angle reflective region 4 having a strong diffusivity.

In addition, as shown in Fig. 5B, when the front light is turned on, the characteristic of the high-direction reflective region 3 becomes dominant, and high luminance is obtained. For a surface light source that irradiates light almost perpendicularly to the liquid crystal panel, such as the front light, a bright display is obtained by the contribution of the specular reflection component of the light 11 from the front light by the highly directional reflecting region 3. to be. Here, the front light may be turned on or automatically turned on by the user according to the degree of ambient light.

In this way, by effectively using the light 11 from the front light for the display, a bright display can be obtained without increasing the light output of the front light, thereby meeting the demand for low power consumption in the reflective liquid crystal display device. Done.

As described above, according to the reflective liquid crystal display device according to the embodiment of the present invention, since the wide viewing angle reflection area 4 and the high-direction reflection area 3 are provided in one display device of the reflection plate, external light Bright displays can be obtained in dominant outdoor and indoor environments where the front lights need to be lit.

On the other hand, in the reflection type liquid crystal display device according to the prior art, the front panel and the reflection type liquid crystal panel are often arranged in the configuration as shown in FIG.

In this case, when the boundary between the wide viewing angle reflective region 4 and the highly directional reflective region 3 of the reflective electrode is parallel to one side of the display device as shown in Fig. 1, the prism groove 12 of the front light is arranged. Direction and the boundary between the reflection areas become the same direction, and moiré due to interference occurs.

6, the linear prism groove 12 of the front light is arranged by arranging the boundary between the wide viewing angle reflective region 4 and the high-directional reflective region 3 to have an L-shaped step. Interference with can be avoided and generation | occurrence | production of a moire can be reduced.

FIG. 7 is a view for explaining a second operation mechanism of the reflective electrode used in the reflective liquid crystal display device according to the embodiment of the present invention.

When the front light is turned off and the reflective liquid crystal display device is used under the external light 10, the external light 10 is usually above the user, on the upper side of the display surface, as shown in FIG.

In this case, as shown in FIG. 7A, when the wide viewing angle reflective region 4 is disposed above the high-directional reflective region 3 in the same display device, the liquid crystal display panel. Of the light incident on the light, the light taken by the light path shown by 2 in FIG. 7A is transmitted through the color filter 13 corresponding to the adjacent pixel. In the drawings, reference numeral 70 denotes a liquid crystal layer.

Therefore, when the adjacent color filters are different colors (R, G, B), light taking this optical path cannot pass through the color filter 13 on the original device. As a result, the brightness of the liquid crystal display panel under external light is reduced.

In contrast, as shown in FIG. 7B, the wide viewing angle reflective region 4 is disposed below the high-directional reflective region 3 with respect to the liquid crystal display panel in the same display apparatus, thereby providing the The light which took the optical path shown by (b) of b) can pass through the color filter 13 corresponding to the same display apparatus, and the said influence can be avoided.

8, the same effect can be obtained by arranging the wide viewing angle reflection region 4 in the center of the display device 2.

9 is a view for explaining a second embodiment according to the present invention.

In the case of the reflective liquid crystal display device, the external light 10 and the light 11 from the front light pass through the same color filter twice, but the white light emitting diode used as the light source of the front light is a light source such as sunlight or a fluorescent lamp. Compared with external light, color is inferior to the display due to external light due to the inferior color rendering and the inability to completely prevent the boundary between the light guide plate and the air or the interface reflection on the surface of the liquid crystal display panel. Lack of reproducibility

In order to improve the color reproducibility at the time of front light lighting, it is effective to prevent the interface reflection and to increase the color density of the color filter. However, when the color density of the whole color filter is made thick, since the transmittance | permeability of a color filter will fall, the problem that the reflectance of the reflection type liquid crystal panel at the time of front light off will fall.

According to the second embodiment of the present invention, as shown in Fig. 9, a high-transmittance color filter corresponds to the high directivity reflective region 3 in the region corresponding to the wide viewing angle reflective region 4 of the reflective electrode. The high chromaticity color filter is divided | segmented and arrange | positioned in the area | region to perform. By arranging the color filters corresponding to the reflection characteristics of the reflecting plate in this way, optimum brightness and color reproducibility are obtained under each environment.

That is, under the external light 10 when the front light is turned off, as shown in FIG. 9 (a), the scattering property of the wide viewing angle reflective region 4 is perpendicular to the liquid crystal display panel deviated from the specular reflection due to the strong reflection property. You can get a bright display at a location close to. At this time, by placing the high transmittance color filter 14 directly above the wide viewing angle reflection region 4, a bright display can be obtained.

On the other hand, when the front light is turned on and used, as shown in Fig. 9B, the light reflected by the high directivity reflective region 3 passes through the high chromaticity color filter 15, and the color A display excellent in reproducibility can be obtained.

Specifically, the high transmittance color filter 14 uses about 20% of the chromaticity region in two passes, and the high chromaticity color filter 15 uses about 40% of the chromaticity region in two passes. Thus, the same chromaticity region (approximately 20%) can be obtained even when the external light is used or when the front light is turned on. As in this embodiment, in the relationship between the high transmittance color filter 14 and the high chromaticity region color filter 15, one in the transmittance and the chromaticity region is high and the other is low.

As described above, according to the present invention, a reflective liquid crystal display device capable of a display sufficiently bright and excellent in color reproducibility can be obtained in any environment such as indoors or dark places where exterior light is dominant and lighting of a front light is required. Can be.

Claims (7)

A first substrate having a plurality of reflective pixel electrodes each having a plurality of reflective regions having different uneven surface structures; A second substrate aligned opposite the first substrate; A liquid crystal inserted between the first substrate and the second substrate; And A front light member aligned to the second substrate side, At least one of the reflective regions has a first reflective characteristic region that reflects incident light from the front light member in a perpendicular direction to the surface of the first substrate, A first average inclination angle of the uneven surface structure of the first reflective characteristic region is different from a second average inclination angle of the uneven surface structure of the remaining reflective region except for the first reflective characteristic region Reflective liquid crystal display device. delete The method of claim 1, And the first average tilt angle is in a range of 1.3 to 3 times the second average tilt angle. The method of claim 1, And the area of the first reflective characteristic region is in a range of 1 to 4 times the area of the remaining reflective regions except for the first reflective characteristic region. The method of claim 1, A boundary between different reflective regions in the reflective pixel electrode is formed in a staircase shape. The method of claim 1, And the first reflective characteristic area is aligned above the display surface in comparison with the remaining reflective areas except for the first reflective characteristic area. The method of claim 1, The second substrate is formed of a first color filter corresponding to the first reflective characteristic region and a second color filter corresponding to the remaining reflective region except for the first reflective characteristic region. The color filter has a higher chromaticity area than the chromaticity area of the second color filter, and the second color filter has a higher transmittance than the first color filter.

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